xbuf_format_converter, used as part of exif_read_data, was appending a terminating null character to the generated string, but was not using its standard append char function. As a result, if the buffer was full, it would result in an out-of-bounds write. 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.
An official patch is available. Apply the patch as soon as possible.
CVSS v4.0 Metrics
Exploitability
Attack VectorNetwork
ComplexityLow
RequirementsPresent
PrivilegesNone
User InteractionNone
Threat
Exploit MaturityUnreported
Vulnerable System
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
Subsequent System
ConfidentialityNone
IntegrityNone
AvailabilityNone
Supplemental
SafetyNegligible
AutomatableYes
RecoveryAutomatic
Value DensityConcentrated
UrgencyMedium
Patch StatusOfficial Patch
Change Log
| Date | Source | Changes | Score |
|---|
| 2026-07-21 | nvd | AV: P→N, AC: H→L, PR: H→N, UI: A→N, VC: N→H, VI: N→H, VA: N→H | 0.0 → 7.2 |
| 2026-07-21 | nvd | patch: Unavailable→Official Patch | 0.0 → 0.0 |
| 2026-07-21 | cve.org | initial, patch: Unavailable | 0.0 |
Affected Software
| Vendor | Product | Version |
|---|
| facebook | hhvm | ≥ 4.57.0, < 4.80.2 |
| facebook | hhvm | ≥ 4.81.0, < 4.93.2 |
| Facebook | HHVM | < 4.56.3 |
| facebook | hhvm | < 4.56.3 |
| Facebook | HHVM | 4.56.3 |
| Facebook | HHVM | 4.57.0 |
| Facebook | HHVM | 4.80.2 |
| Facebook | HHVM | 4.81.0 |
| Facebook | HHVM | 4.93.2 |
| facebook | hhvm | 4.94.0 |
| Facebook | HHVM | 4.94.0 |
| Facebook | HHVM | 4.94.1 |
| Facebook | HHVM | 4.95.0 |
| facebook | hhvm | 4.95.0 |
| Facebook | HHVM | 4.95.1 |
| facebook | hhvm | 4.96.0 |
| Facebook | HHVM | 4.96.0 |
| Facebook | HHVM | 4.96.1 |
| facebook | hhvm | 4.97.0 |
| Facebook | HHVM | 4.97.0 |
| Facebook | HHVM | 4.97.1 |
| Facebook | HHVM | 4.98.0 |
| facebook | hhvm | 4.98.0 |
| Facebook | HHVM | 4.98.1 |
Published: 2021-03-10
