CVE-2021-27419Network attack vector

Code execution or crash via allocation wrap-around

Published May 3, 2022 · Updated Apr 16, 2025

Integer overflow in uClibc-ng before 1.0.37 allows remote attackers to crash or execute code via oversized allocation requests. The malloc and memalign paths in libc/stdlib/malloc-simple/alloc.c fail to reject sizes above PTRDIFF_MAX or a wrapped size-plus-alignment calculation before allocation. Remote impact requires a linked application to pass attacker-controlled allocation sizes; successful triggering can crash that process or execute code in its context.

CVSS severity9.8
Critical
EPSS probability1.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in uClibc-ng before 1.0.37 allows remote attackers to crash or execute code via oversized allocation requests. The malloc and memalign paths in libc/stdlib/malloc-simple/alloc.c fail to reject sizes above PTRDIFF_MAX or a wrapped size-plus-alignment calculation before allocation. Remote impact requires a linked application to pass attacker-controlled allocation sizes; successful triggering can crash that process or execute code in its context.

The record

CVE
CVE-2021-27419
Published
May 3, 2022
Updated
Apr 16, 2025
Vendor
uClibc-ng
Product
uClibc-ng
Classifications
CWE-190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 3, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.0.37

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

uClibc-ng · uClibc-ngversion=unspecified <1.0.37

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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