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High, CVSS 8.4amended

OpenEXR: integer overflow to OOB write in uncompress_b44_impl()

CVE-2026-34544GHSA-h762-rhv3-h25v

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI openexr

    Affected
    >= 3.4.0, <= 3.4.7>= 3.3.0, <= 3.3.8>= 3.2.0, <= 3.2.6
    Fixed in
    3.4.8

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.4 · CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-34544: 0.25% estimated exploitation activity in the next 30 days; percentile 16.95 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary The B44/B44A decoder in OpenEXR reconstructs row pointers into a scratch buffer using int. When the channel width (nx) is large enough, the product y nx overflows int, causing the row pointer to wrap before the start of the scratch buffer. Subsequent memcpy() calls then write decoded pixel blocks to an invalid address, producing an active out-of-bounds write. Root cause Variable declarations (internalb44.c:535) nx and ny are declared as plain int. They are assigned from curc-width and curc-height which are int32t. Scratch buffer allocation (internalb44:543) The allocation path correctly promotes to uint64t before multiplying. The scratch buffer is always large enough to hold the full channel. Row pointer reconstruction (internalb44:560) y and nx are both int. The product y nx is computed in int. If this product exceeds INTMAX (2,147,483,647), the result is signed integer overflow Out of Band write (internalb44:592) These four writes copy decoded B44 pixel blocks into…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-h762-rhv3-h25v

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-h762-rhv3-h25v

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-34544

Advisory: OpenEXR: integer overflow to OOB write in uncompress_b44_impl()
IDs: CVE-2026-34544, GHSA-h762-rhv3-h25v
Record: https://patchnext.com/advisories/cve-2026-34544 (revision 3, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: openexr 3.4.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI openexr: affected >= 3.4.0, <= 3.4.7; >= 3.3.0, <= 3.3.8; >= 3.2.0, <= 3.2.6; fixed in 3.4.8

## Suggested inspection (read-only)
- `python -m pip show openexr`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on openexr.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-h762-rhv3-h25v (OSV record GHSA-h762-rhv3-h25v lists affected ranges: PyPI openexr >=3.4.0 =3.3.0 =3.2.0 <=3.2.6)
- Verified: https://github.com/advisories/GHSA-h762-rhv3-h25v (GitHub-reviewed advisory GHSA-h762-rhv3-h25v lists affected ranges: PyPI openexr >=3.4.0 =3.3.0 =3.2.0 <=3.2.6)

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