CVE-2021-29325: OpenSource Moddable v10.5.0 was discovered to contain a heap buffer overflow in the fx_String_prototype_repeat

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HIGH 7.8DOWNGRADE

CVE-2021-29325 is a high-severity flaw (CVSS 7.8) affecting moddable. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OpenSource Moddable v10.5.0 was discovered to contain a heap buffer overflow in the fx_String_prototype_repeat function at /moddable/xs/sources/xsString.c.

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.8% (top 45%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-11-19
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: moddable

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-11-19 17:15 UTCPublished CVE record published
2026-06-17 03:47 UTCUpdated Record last modified

moddable moddable DOWNGRADE

Affected: 10.5.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.5.0

1. Check installed version

apt-cache policy moddable || rpm -q moddable || moddable --version

2. No fixed release: DOWNGRADE to a release before 10.5.0 (Debian / Ubuntu)

apt-cache madison moddable sudo apt install moddable=<VERSION_BEFORE_10.5.0> sudo apt-mark hold moddable

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list moddable sudo dnf downgrade moddable-<VERSION_BEFORE_10.5.0> sudo dnf versionlock add moddable

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-29325?

moddable: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-29325 being exploited?

CVE-2021-29325 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-29325 affect?

CVE-2021-29325 affects moddable. Severity is high (CVSS 7.8). OpenSource Moddable v10.5.0 was discovered to contain a heap buffer overflow in the fx_String_prototype_repeat function at /moddable/xs/sources/xsString.c.

How urgent is CVE-2021-29325?

Priority 46/100. High severity; Public exploit reference

Related CVEs

CVE-2022-29368 HIGH 7.1 UPGRADE Moddable commit before 135aa9a4a6a9b49b60aa730ebc3bcc6247d75c45 was discovered to contain an out-of-bounds rea
CVE-2021-29329 HIGH 7.8 DOWNGRADE OpenSource Moddable v10.5.0 was discovered to contain a stack overflow in the fxBinaryExpressionNodeDistribute
CVE-2021-29328 HIGH 7.1 DOWNGRADE OpenSource Moddable v10.5.0 was discovered to contain buffer over-read in the fxDebugThrow function at /moddab
CVE-2021-29327 HIGH 7.8 DOWNGRADE OpenSource Moddable v10.5.0 was discovered to contain a heap buffer overflow in the fx_ArrayBuffer function at
CVE-2021-29326 HIGH 7.8 DOWNGRADE OpenSource Moddable v10.5.0 was discovered to contain a heap buffer overflow in the fxIDToString function at /

References

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