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CVE Record

CVE-2026-27809: psd-tools: Compression module has unguarded zlib decompression, missing dimension validation, and hardening gaps

psd-tools is a Python package for working with Adobe Photoshop PSD files. Prior to version 1.12.2, when a PSD file contains malformed RLE-compressed image data (e.g. a literal run that extends past the expected row size), decode_rle() raises ValueError which propagated all the way to the user, crashing psd.composite() and psd-tools export. decompress() already had a fallback that replaces failed channels with black pixels when result is None, but it never triggered because the ValueError from decode_rle() was not caught. The fix in version 1.12.2 wraps the decode_rle() call in a try/except so the existing fallback handles the error gracefully.

MediumCVSS 6.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2026-27809 affects psd-tools, a Python library used to process Photoshop PSD files. Before 1.12.2, certain malformed compressed PSD image data can crash composition or export workflows instead of being handled gracefully. Business risk is mainly disruption to services or automation that process PSD files, especially if users can upload or submit files.

Executive priority

Treat as a medium-priority availability issue. Patch promptly in file-processing services exposed to customers or partners. Lower urgency applies to internal-only tools processing trusted PSDs, but upgrading remains the cleanest risk reduction.

Technical view

In psd-tools versions before 1.12.2, malformed RLE-compressed image data can cause decode_rle() to raise ValueError. That exception was not caught, so psd.composite() and export operations could crash. Version 1.12.2 wraps decode_rle() with exception handling so the existing fallback can replace failed channels with black pixels.

Likely exposure

Exposure is likely in applications, workers, or media pipelines using psd-tools below 1.12.2 to process PSD files. Risk increases when PSD files come from untrusted users, external partners, or automated ingestion channels.

Exploitation context

The source bundle does not indicate active exploitation, and the CVE is not marked as CISA KEV. The issue appears triggerable through malformed PSD content processed by vulnerable psd-tools code. No exploit details are needed to understand exposure.

Researcher notes

The public description centers on uncaught ValueError handling in RLE decompression. The title references broader decompression and validation hardening gaps, but provided details identify the concrete fix as catching decode_rle() failures and using the existing fallback path.

Mitigation direction

  • Upgrade psd-tools to version 1.12.2 or later.
  • Prioritize systems processing untrusted or user-supplied PSD files.
  • Restrict PSD ingestion where upgrades cannot be completed promptly.
  • Check the GitHub advisory and release notes for current vendor guidance.

Validation and detection

  • Inventory Python environments for psd-tools usage.
  • Confirm installed psd-tools versions are 1.12.2 or later.
  • Review upload, conversion, and export services that process PSD files.
  • Monitor logs for PSD processing crashes or repeated ValueError failures.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-190: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-409: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-617: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-704: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-755: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-789: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.8 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
6.8CVSS 4.0MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:U——Primary CVE score

Vulnerability scoring details

Base CVSS 4.0 score

6.8Medium
CVSS 4.0 vector shape for CVE-2026-27809Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
psd-toolspsd-tools< 1.12.2Listed
Weakness

CWE details

CWE-190CWE-409CWE-617CWE-704CWE-755CWE-789

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.