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CVE-2021-24036· NVD / CVE Program· CNA facebook

Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with

Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds write on the heap with the possibility of remote code execution. This issue affects versions of folly prior to v2021.07.22.00. This issue affects HHVM versions prior to 4.80.5, all versions between 4.81.0 and 4.102.1, all versions between 4.103.0 and 4.113.0, and versions 4.114.0, 4.115.0, 4.116.0, 4.117.0, 4.118.0 and 4.118.1.

CriticalCVSS 9.8 · v3.1—No exploit No fix recorded
Published
Jul 22, 2021
Updated
Jun 16, 2026
EPSS
3.3% · 88th percentile
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Report tools

JSON

Action score

40

Plan

Add it to your regular patch cycle.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 3.3%

Affected systems

VendorProduct
facebookfolly
facebookhhvm

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • facebook follybefore 2021.07.22.00
  • facebook hhvmbefore 4.80.5
  • facebook hhvm4.81.0 and later · up to 4.102.1 inclusive
  • facebook hhvm4.103.0 and later · up to 4.113.0 inclusive
  • facebook hhvm4.114.0
  • facebook hhvm4.115.0
  • facebook hhvm4.116.0
  • facebook hhvm4.117.0
  • facebook hhvm4.118.0
  • facebook hhvm4.118.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (facebook). Independent of NVD's CPE analysis and usually ahead of it.

  • Facebook folly

    • v2021.07.22.00 and later · before unspecifiednot affected
    • unspecified and later · before v2021.07.22.00affected

  • Facebook HHVM

    • 4.117.0, 4.116.0, 4.115.0, 4.114.0, 4.113.0affected
    • 4.118.2 and later · before unspecifiednot affected
    • 4.118.0 and later · before unspecifiedaffected
    • 4.117.1 and later · before unspecifiednot affected
    • 4.116.1 and later · before unspecifiednot affected
    • 4.115.1 and later · before unspecifiednot affected
    • 4.114.1 and later · before unspecifiednot affected
    • 4.113.1 and later · before unspecifiednot affected
    • 4.102.2 and later · before unspecifiednot affected
    • 4.102.0 and later · before unspecifiedaffected

Same product

facebook: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-11934Improper handling of close_notify alerts can result in an out-of-bounds read in AsyncSSLSocket.
    40Plan
  • CVE-2018-6337folly::secureRandom will re-use a buffer between parent and child processes when fork() is called.
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-122 · Heap-based Buffer Overflow

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records