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Vulnerabilities

Security fix · GHSA-f2hq-32vh-53cc

postal-mime: Quadratic CPU consumption when decoding a header of many joinable RFC 2047 base64 encoded words

Published Oct 23, 2026 · catalog updated Oct 23, 2026 · postal-mime: Quadratic CPU consumption

Last checked Oct 24, 2026, 12 days ago.

Open the advisory

Exploitation likelihood is not on this record for GHSA-f2hq-32vh-53cc. A missing EPSS score is not a low risk. Compare postal-mime: Quadratic CPU consumption with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (postal-mime: Quadratic CPU consumption).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Version ranges on file
Affected products
npm postal-mime

### Impact Decoding a header that holds a long run of joinable RFC 2047 base64 encoded words, such as repeated tens of thousands of times in a , , , a filename or a description, took time quadratic in the number of words. The join check ran a regex over the text joined so far for every word, which flattens the accumulated string each time. A single well formed message of about 1.6 MB blocked the event loop for one to twenty seconds depending on the host, and inline parts multiplied the cost, since each nested message carried its own header budget. Any application that parses untrusted mail with postal-mime 3.0.0 through 4.0.7, including the exported helper, is affected. There is no confidentiality or integrity impact. ### Patches Fixed in 4.0.8. The pad check now tracks the last appended word instead of testing the joined text, so decoding is linear in the header length. The same release also counts the parts and header bytes of inline sub-messages against the limits of the message as a whole, counts every header line for at least 64 bytes of , and adds a scaling test that measures every stage of the parser at two input sizes. ### Workarounds Lower from its 2 MiB default to bound the cost per message, or parse untrusted mail in a worker that can be terminated. ### Credits Reported by Felipe Fernández.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • npm postal-mime>= 3.0.0, < 4.0.8

How to fix GHSA-f2hq-32vh-53cc

  • Upgrade

    GHSA-f2hq-32vh-53cc lists a fix boundary at 4.0.8. Compare the installed build with that boundary before you change production.

  • Version check

    Affected < 4.0.8

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for GHSA-f2hq-32vh-53cc. A missing EPSS score is not a low risk. Compare postal-mime: Quadratic CPU consumption with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with >= 3.0.0, < 4.0.8. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-400: Uncontrolled Resource Consumption; CWE-407. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 23, 2026 · GitHub Advisory Database

    Detected

    ### Impact Decoding a header that holds a long run of joinable RFC 2047 base64 encoded words, such as repeated tens of thousands of times in a , , , a filename or a description, took time quadratic in the number of words. The join check ran a regex over the text joined so far for every word, which flattens the accumulated string each time. A single well formed message of about 1.6 MB blocked the e

  2. Oct 23, 2026 · GitHub Advisory Database

    Updated

    ### Impact Decoding a header that holds a long run of joinable RFC 2047 base64 encoded words, such as repeated tens of thousands of times in a , , , a filename or a description, took time quadratic in the number of words. The join check ran a regex over the text joined so far for every word, which flattens the accumulated string each time. A single well formed message of about 1.6 MB blocked the e

Sources

  • GitHub Advisory DatabasePackage advisoryGHSA-f2hq-32vh-53cc

    postal-mime: Quadratic CPU consumption when decoding a header of many joinable RFC 2047 base64 encoded words

    github.com

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitHub Advisory DatabaseOct 24, 2026