CVE-2026-62438

Executive Summary

CVE-2026-62438 is an integer overflow vulnerability (CWE-190) in the GIMP image manipulation suite, triggered when a user opens or previews a specially crafted Bohemia Interactive (PAA) texture file. Because image dimensions are computed from untrusted file metadata during decompression, an attacker can force the allocation of an undersized heap buffer, which is subsequently over-read during processing — crashing the PAA plug-in process and potentially leaking adjacent memory contents. The flaw is remotely deliverable but requires user interaction (CVSS 6.1, AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H); no public proof-of-concept or exploit code exists at time of writing and the vulnerability is unpatched.

Technical Analysis

CVE-2026-62438 resides in GIMP's handling of the Bohemia Interactive PAA texture format — a container format used by the Arma and DayZ engine families that stores compressed mipmapped texture data alongside dimension metadata. Per the NVD description, the defect is an integer overflow that occurs "when calculating image dimensions during file decompression." The application derives buffer sizing from those computed dimensions; the arithmetic overflow yields a small or wrapped value, so the allocated buffer is smaller than the amount of data the decompressor subsequently writes or the downstream processor subsequently reads.

Two distinct fault conditions follow from the same root cause and are described in the advisory:

1. Out-of-bounds read leading to information disclosure. After the undersized buffer is populated (or under-populated), subsequent processing reads past the buffer boundary. Because the read is not terminated by a boundary check, data beyond the allocation may be interpreted as image content and could be surfaced in the application or otherwise mishandled, constituting the "potentially disclose sensitive memory contents" impact class.
2. Denial of service via abnormal termination. The over-read manifests in a crash of the plug-in process, which the description states terminates "unexpectedly." In GIMP's architecture, format handlers run as separate plug-in processes; the crash aborts the import operation and may terminate any unsaved editor state the plug-in was servicing.

The CVSS vector is internally consistent with this mechanism: AC:L reflects that no race or timing precision is required once a malformed file exists; UI:R reflects that the victim must open or preview the file; A:H reflects the reliable process termination; C:L reflects that the disclosure is opportunistic (adjacent heap contents rather than a controlled read primitive at an arbitrary address).

Critical forensic caveat: the supplied intelligence provides no function names, file paths, exact size-threshold values, or affected version ranges. The precise arithmetic expression that wraps, the field of the PAA header that carries the malicious dimensions, and the patch commit are all unavailable. Any report claiming a specific function (e.g., a named loader routine) or a specific overflow width would be fabricating detail. What is technically defensible is the class: unchecked multiplication/addition of attacker-controlled dimension integers before a heap allocation, followed by a length-unchecked read.

The attack surface is the PAA loader reached through: (a) File → Open on a .paa file, (b) any thumbnail/preview path in the file chooser that renders PAA thumbnails, and (c) batch/non-interactive invocations that feed PAA files to the loader. Because thumbnailing can occur without an explicit "open," the preview surface marginally increases exposure relative to open-only workflows.

Exploitation Scenarios

No public PoC is available; the chain below is inferred from the vulnerability class (CWE-190 → undersized allocation → over-read) and the advisory text. No specific implementation identifiers are asserted.

Step 1 — Reconnaissance / target identification. The attacker does not need to discover victims individually; PAA is a modding and game-asset format, so targets are self-selecting communities — game modders, texture artists, Arma/DayZ asset pipelines, and GIMP users who exchange source art. Delivery infrastructure is generic: mod repositories, asset-sharing forums, Discord file drops, and email attachments. The attacker needs only one victim running a GIMP build that includes the PAA plug-in.

Step 2 — Trigger of the specific flaw class. The attacker crafts a PAA file in which the encoded dimension metadata, when processed by the decompression arithmetic, overflows — i.e., the computed allocation size wraps to a small integer relative to the true decompressed extent. No malformed-length trick beyond dimension manipulation is required; the file can otherwise be structurally plausible, which is why preview/thumbnail generation is a viable trigger: the victim need not even complete a full open.

Step 3 — Execution at the vulnerability-class level. When the victim opens or previews the file, the loader computes dimensions, allocates the wrapped (undersized) buffer, and begins decompression/processing. Processing proceeds past the true end of the allocated region — an out-of-bounds read. There is no write primitive described and no code-execution claim; the payload objective is the read itself plus the crash.

Step 4 — Post-exploitation impact. Two outcomes: (a) the plug-in process terminates, destroying in-progress work and, in automated pipelines, halting batch jobs — the availability impact; (b) heap-adjacent contents beyond the buffer may be exposed in the disclosed/rendered output — the confidentiality impact. There is no described persistence, privilege escalation, or lateral movement primitive; this is a client-side, user-interaction-gated fault, and attempts to characterize it as an RCE chain would be unsupported.

Impact Assessment

Confidentiality (C:L). The over-read may expose memory adjacent to the allocation. In the GIMP plug-in context this memory could include fragments of previously processed image data or other process-resident content. The advisory qualifies this as "potentially," and the CVSS rating of Low reflects that the disclosure is not a clean, repeatable arbitrary-read primitive.

Integrity (I:N). No integrity impact is described. The defect does not corrupt the opened document or persisted files through the described mechanism.

Availability (A:H). The most concrete and reproducible impact: the plug-in process terminates unexpectedly. For an interactive user this means loss of the import operation and potentially unsaved editor state; for automated or batch workflows it means hard job failure. A:H is appropriate because the crash is reliable once a suitable file is crafted, not probabilistic.

Scope (S:U). Impact is confined to the plug-in process and the user's GIMP session; no scope change to the host OS is described.

Blast radius. Individual workstations running affected GIMP builds with the PAA loader — not servers, not network services. The realistic enterprise exposure is narrow but non-zero: design, marketing, and game-development workstations where GIMP is installed and where untrusted art assets are routinely ingested. Asset-review pipelines that auto-thumbnail uploaded files are the highest-leverage target because they remove the human judgment step that would otherwise filter suspicious files.

Threat context. CISA KEV status: not listed. EPSS: not scored by FIRST.org — no exploitation-probability estimate exists and none should be assumed. No exploit code or Nuclei template is publicly tracked. Current risk is therefore driven by the unpatched state and the low skill floor of file-format DoS crafting, not by observed exploitation.

Detection Guidance

Sigma Rule

title: GIMP PAA Plug-in Crash Indicative of Integer Overflow (CVE-2026-62438)
id: 8f3c2a91-6243-4c1e-9b7a-0d5e1a624381
status: experimental
description: Detects abnormal termination of a GIMP plug-in process following PAA file processing, consistent with the undersized-buffer over-read in CVE-2026-62438.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-62438
author: valtersit.com threat intelligence
date: 2026/01/01
logsource:
  category: process_termination
  product: linux
detection:
  selection_image:
    Image|endswith:
      - '/gimp'
      - '/gimp-2.10'
      - '/gimp-3.0'
  selection_fault:
    ExitCode:
      - 139
      - 134
      - 11
  selection_parent_or_cmd:
    ParentImage|endswith:
      - '/gimp'
      - '/gimp-2.10'
      - '/gimp-3.0'
  condition: selection_fault and (selection_parent_or_cmd or selection_image)
falsepositives:
  - Legitimate plug-in crashes from unrelated malformed files
  - Out-of-memory kills during very large legitimate image operations
level: low
tags:
  - attack.t1204.002
  - cve.2026.62438

YARA Rule

rule CVE_2026_62438_GIMP_PAA_Dimension_Overflow
{
    meta:
        description = "Heuristic detection of PAA texture files with dimension metadata prone to integer overflow in GIMP's PAA loader"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-62438"
        author = "valtersit.com threat intelligence"
        date = "2026-01-01"
        severity = "medium"

    strings:
        $paa_magic = { 44 44 53 20 }        // "DDS " header magic common to PAA/ DDS lineage
        $paa_magic2 = { 50 41 41 00 }       // "PAA\0" literal marker
        $ext = ".paa" ascii nocase

    condition:
        (uint32(0) == 0x20534444 or $paa_magic or $paa_magic2) and
        filesize < 200MB
}

Note: YARA is a file-content matcher and cannot evaluate arithmetic overflow conditions at scan time. The rule above is a triage filter for PAA-bearing artifacts in mail gateways and file shares; it must be paired with sandboxed rendering (see Mitigation) rather than treated as a positive verdict.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-62438 GIMP PAA texture file transfer (possible integer overflow trigger)"; flow:established,to_client; file_data; content:"DDS "; depth:4; fileext:"paa"; filestore; sid:2026624380; rev:1; metadata:cve CVE-2026-62438, affected_product GIMP, attack_target Client_Endpoint, deployment Perimeter, signature_severity Minor; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-62438; classtype:attempted-user;)

This rule flags inbound PAA file transfers for quarantine/inspection; it identifies delivery of the attack file class, not the overflow itself, which occurs on the host.

Elastic Detection

process where event.type == "end" and
  process.exit_code in (11, 134, 139) and
  (process.parent.name like~ "gimp*" or process.name like~ "gimp*")

To reduce noise, pair with a preceding file where file.extension == "paa" event in the same sequence by host.id with maxspan=5m block.

Splunk SPL Query

index=endpoint (EventCode=4689 OR sourcetype="linux:syslog" OR sourcetype="WinEventLog:Security")
| eval proc=coalesce(Image, process_name, comm)
| where like(proc, "%gimp%")
| join type=left host [
    search index=endpoint sourcetype="*filesystem*" file_extension=paa
    | stats latest(_time) as paa_time by host
  ]
| where exit_status IN ("139","134","11","-1073741819") OR status="crashed"
| table _time host proc exit_status paa_time

Adjust index/sourcetype to your environment; the query correlates GIMP process exits with recent PAA file activity on the same host.

Wazuh OSSEC Rule

<group name="gimp,cve-2026-62438,">
  <rule id="100624" level="7">
    <if_sid>5501,5502</if_sid>
    <match>gimp</match>
    <regex>segfault|Segmentation fault|signal 11|signal 6</regex>
    <description>CVE-2026-62438: GIMP process crashed while processing image data (possible PAA integer overflow)</description>
    <mitre>
      <id>T1204.002</id>
    </mitre>
  </rule>
  <rule id="100625" level="3">
    <if_sid>100624</if_sid>
    <match>\.paa</match>
    <description>CVE-2026-62438 correlation: PAA file referenced in GIMP crash context</description>
  </rule>
</group>

Rule IDs are site-local placeholders (100624–100625); renumber to fit your allocation.

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No vendor fix, patch reference, or affected version range has been published in tracked sources. The absence of a fixed version means the following is interim risk management, not remediation.

1) Immediate mitigations

• Disable or isolate the PAA loader. In GIMP, restrict the plug-in search path (Preferences → Folders → Plug-ins) so the PAA plug-in directory is excluded, or remove/move the PAA plug-in binary from the installation's plug-in directory. This is the single highest-efficacy control because it removes the attack surface entirely. Validate that PAA files no longer open and that no other workflow depends on them.
• Intercept PAA files at the perimeter. Block or quarantine .paa attachments at mail gateways and file-transfer services for user populations that do not legitimately require the format; enforce the Suricata filestore rule above to capture samples for analysis.
• Neutralize the preview path. Disable thumbnail generation for unknown/untrusted file types in the file chooser, or restrict users from browsing untrusted directories in GIMP. Preview triggers the loader without an explicit open, lowering the interaction bar.
• Sandbox the editor. Run GIMP in a container or low-privilege account without access to sensitive network shares or credential stores, reducing the value of any memory disclosure and the blast radius of a plug-in compromise.
• Asset pipeline controls. Any automated service that renders or thumbnails uploaded images should process PAA in a disposable sandbox with resource limits and no access to persistent storage.

2) Patch / upgrade steps

• Monitor the GIMP project's security advisories and release notes for a version that address CVE-2026-62438; no fixed release is currently identified. Treat any version claim as unverified until confirmed against the vendor's own advisory.
• When a fixed build ships, stage it in a pilot group and verify PAA import behaves normally before fleet deployment.
• Maintain an inventory of GIMP installations (workstation agents, package manifests) so the fix can be pushed quickly; unmanaged or self-installed copies in design and modding teams are the likely blind spot.

3) Long-term hardening

• Prefer default-deny plug-in allowlisting: only plug-ins required for sanctioned workflows should be present on production workstations. GIMP's plug-in model gives each format handler significant trust; treat it as an extension surface to be minimized.
• Extend file-type allowlisting at email and web gateways to include niche game-asset formats (PAA among them), not just executables and office documents.
• Integrate file-format fuzzing into the acceptance criteria for any tool that ingests third-party assets; the integer-overflow-during-decompression class is a fuzzing target, not an exotic case.
• Retain crash telemetry (core dumps excluded from upload where sensitive) for a defined window to support retrospective triage if a targeted campaign is later identified.

References

1. NVD — CVE-2026-62438: https://nvd.nist.gov/vuln/detail/CVE-2026-62438
2. MITRE CWE-190 — Integer Overflow or Wraparound: https://cwe.mitre.org/data/definitions/190.html
3. MITRE ATT&CK T1204.002 — User Execution: Malicious File: https://attack.mitre.org/techniques/T1204/002/
4. FIRST EPSS — no score currently published for this CVE: https://www.first.org/epss/
5. CISA Known Exploited Vulnerabilities Catalog — CVE-2026-62438 is not listed: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor and in-the-wild status: No exploitation in the wild is reported. No threat actor campaign has been publicly attributed to this CVE. CISA KEV: not listed. EPSS: unscored. PoC/exploit code: none publicly tracked. The assessment of risk rests on the unpatched state and the low barrier to crafting malformed file-format inputs, not on observed adversary activity.