CVE-2020-1921: facebook hhvm Stack-based Buffer Overflow
Vulnerability summary
CVE-2020-1921 is a high (CVSS 7.5) Stack-based Buffer Overflow vulnerability in facebook hhvm. EPSS estimates a 1.21% chance of exploitation in the next 30 days, higher than 68.1% of scored vulnerabilities.
Timeline
- 10-03-2021PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
Description
In the crypt function, we attempt to null terminate a buffer using the size of the input salt without validating that the offset is within the buffer. This issue affects HHVM versions prior to 4.56.3, all versions between 4.57.0 and 4.80.1, all versions between 4.81.0 and 4.93.1, and versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0.
CVSS metrics
3 scores · 2 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
1.21%
Chance of exploitation in the next 30 days
Percentile
68%
Versus all other CVEs
30-day change
0.00 pp
From 1.21% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-121Stack-based Buffer OverflowA stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).
- CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.
Affected systems
Facebook1 product
- hhvm≥ 4.81.0, < unspecified | ≥ 4.57.0, < unspecified | ≥ unspecified, < 4.56.3 | < 4.56.3 | ≥ 4.57.0, < 4.80.2 | ≥ 4.81.0, < 4.93.2 | 4.94.0 | 4.95.0 | 4.96.0 | 4.97.0 | 4.98.0
Ubuntu1 product
- hhvmAll versions (No fix recorded)
2 vendors · 2 products
References
4 links- github.com/facebook/hhvm/commit/08193b7f0cd3910256e00d599f0f3eb2519c44caX Refsource MISCREPORTPatchThird Party Advisory