CVE-2022-40896

Process hang via Smithy metadata regex backtracking

Published Jul 19, 2023 · Updated Nov 27, 2024

Regular expression denial of service in Pygments before 2.15.0 allows attackers to hang a consuming process with crafted Smithy text. SmithyLexer's metadata rule uses an overlapping greedy match for the metadata name before the equals sign, causing catastrophic backtracking on crafted input. A user or application must pass the text to SmithyLexer, after which regex evaluation can consume CPU and stall the process.

CVSS severity5.5
Medium
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Pygments before 2.15.0 allows attackers to hang a consuming process with crafted Smithy text. SmithyLexer's metadata rule uses an overlapping greedy match for the metadata name before the equals sign, causing catastrophic backtracking on crafted input. A user or application must pass the text to SmithyLexer, after which regex evaluation can consume CPU and stall the process.

The record

CVE
CVE-2022-40896
Published
Jul 19, 2023
Updated
Nov 27, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 19, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 27, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.8GitHubCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
5.5NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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