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CVE Record

CVE-2021-35525: PostSRSd before 1.11 allows a denial of service (subprocess hang) if Postfix sends certain long data fields...

PostSRSd before 1.11 allows a denial of service (subprocess hang) if Postfix sends certain long data fields such as multiple concatenated email addresses. NOTE: the PostSRSd maintainer acknowledges "theoretically, this error should never occur ... I'm not sure if there's a reliable way to trigger this condition by an external attacker, but it is a security bug in PostSRSd nevertheless."

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This issue affects PostSRSd, a mail forwarding support component. Certain unusually long address data passed by Postfix can make a PostSRSd subprocess hang, potentially disrupting mail handling. The sources describe denial of service, not data theft or remote code execution.

Executive priority

Treat as a moderate operational availability risk for affected mail infrastructure. Prioritize remediation on production mail relays, but do not treat it as confirmed actively exploited based on the supplied sources.

Technical view

PostSRSd before 1.11 can hang a subprocess when Postfix sends certain long data fields, such as multiple concatenated email addresses. The maintainer stated the condition should theoretically never occur and external trigger reliability is unclear, but treated it as a security bug.

Likely exposure

Exposure is most relevant to mail servers using Postfix with PostSRSd versions before 1.11. The supplied CVE data does not enumerate affected distributions or configurations beyond PostSRSd and Gentoo advisory references.

Exploitation context

The source bundle does not show active exploitation, and CISA KEV status is false. Exploitability from an external attacker is uncertain because the maintainer questioned whether the triggering condition is reliably reachable externally.

Researcher notes

Evidence is limited: no CVSS, CWE, or reliable external trigger details are provided. Focus validation on version exposure and operational symptoms rather than exploit reproduction. Avoid assuming affected products beyond PostSRSd before 1.11.

Mitigation direction

  • Upgrade PostSRSd to version 1.11 or a vendor-patched package.
  • Review Gentoo GLSA-202107-08 if using Gentoo-managed packages.
  • Check current vendor guidance for supported package versions.
  • Prioritize mail systems where PostSRSd handles production forwarding traffic.

Validation and detection

  • Inventory systems running PostSRSd with Postfix.
  • Confirm installed PostSRSd versions are 1.11 or vendor-patched.
  • Review mail service monitoring for PostSRSd hangs or stalled subprocesses.
  • Verify package management records show the security update applied.
Prepared
Confidence
medium
Sources
6

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

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CVE-2021-35525 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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