CVE-2021-29939Public exploitNetwork attack vector

Stack memory corruption via inconsistent iterator bounds

Published Apr 1, 2021 · Updated Nov 19, 2024

Out-of-bounds write in stackvector before 1.0.9 allows attackers to corrupt stack memory through a malformed Iterator size hint. StackVec::extend validates capacity against the reported upper bound but writes up to the lower bound without enforcing their order. Exploitation requires a caller-supplied Iterator whose lower bound exceeds its upper bound, causing a stack overwrite and a crash or corrupted program state.

CVSS severity7.3
High
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in stackvector before 1.0.9 allows attackers to corrupt stack memory through a malformed Iterator size hint. StackVec::extend validates capacity against the reported upper bound but writes up to the lower bound without enforcing their order. Exploitation requires a caller-supplied Iterator whose lower bound exceeds its upper bound, causing a stack overwrite and a crash or corrupted program state.

The record

CVE
CVE-2021-29939
Published
Apr 1, 2021
Updated
Nov 19, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 19, 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.3GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.3NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.3RustSec Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.5NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-787Out-of-bounds Write

Public exploit references

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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