php: Overflowing the length of string causes crash
Published May 12, 2017
9.8
CRITICALCVSS 3.1
EPSS 7.19%
Description
The zend_string_extend function in Zend/zend_string.h in PHP through 7.1.5 does not prevent changes to string objects that result in a negative length, which allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact by leveraging a script's use of .= with a long string.
Affected products
No data.
No data.
Red Hat Enterprise Linux 8
php:7.4-8080020230118140634.cc342424
Fixed · RHSA-2023:2903
Red Hat Enterprise Linux 5
php
Not affected
Red Hat Enterprise Linux 5
php53
Not affected
Red Hat Enterprise Linux 6
php
Not affected
Red Hat Enterprise Linux 7
php
Not affected
Red Hat Enterprise Linux 8
php:7.3/php
Affected
Red Hat Software Collections
rh-php56-php
Not affected
Red Hat Software Collections
rh-php70-php
Will not fix
Red Hat Software Collections
rh-php73-php
Will not fix
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 8 | php:7.4-8080020230118140634.cc342424 | Fixed | RHSA-2023:2903 |
| Red Hat Enterprise Linux 5 | php | Not affected | n/a |
| Red Hat Enterprise Linux 5 | php53 | Not affected | n/a |
| Red Hat Enterprise Linux 6 | php | Not affected | n/a |
| Red Hat Enterprise Linux 7 | php | Not affected | n/a |
| Red Hat Enterprise Linux 8 | php:7.3/php | Affected | n/a |
| Red Hat Software Collections | rh-php56-php | Not affected | n/a |
| Red Hat Software Collections | rh-php70-php | Will not fix | n/a |
| Red Hat Software Collections | rh-php73-php | Will not fix | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
This issue is only practical to exploit on 32-bit systems, and then only when the memory limit is raised from its default to a value larger than 2 GiB. The default settings make exploitation impossible. For these reasons, PHP upstream developers do not consider this to be a security issue. Red Hat Software Collections and Red Hat Enterprise Linux 7 and later only distribute PHP built for 64-bit systems.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
AV:N/AC:L/Au:N/C:P/I:P/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2021–2026- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v1
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (47 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 7.19% (0.07191) | 94.12th | v5 (v2026.06.15) |
| Jun 15, 2026 | 7.19% (0.07191) | 93.48th | v5 (v2026.06.15) |
| Mar 4, 2026 | 4.59% (0.04586) | 89.01th | v4 (v2025.03.14) |
| Mar 1, 2026 | 2.50% (0.02495) | 85.12th | v4 (v2025.03.14) |
| Feb 4, 2026 | 4.59% (0.04586) | 88.95th | v4 (v2025.03.14) |
| Feb 1, 2026 | 2.50% (0.02495) | 85.02th | v4 (v2025.03.14) |
| Jan 4, 2026 | 4.59% (0.04586) | 88.88th | v4 (v2025.03.14) |
| Jan 1, 2026 | 2.50% (0.02495) | 84.98th | v4 (v2025.03.14) |
| Dec 28, 2025 | 4.59% (0.04586) | 88.87th | v4 (v2025.03.14) |
| Dec 27, 2025 | 3.04% (0.03038) | 86.30th | v4 (v2025.03.14) |
| Dec 4, 2025 | 4.59% (0.04586) | 88.80th | v4 (v2025.03.14) |
| Dec 1, 2025 | 2.50% (0.02495) | 84.89th | v4 (v2025.03.14) |
| Nov 21, 2025 | 4.59% (0.04586) | 88.74th | v4 (v2025.03.14) |
| Nov 18, 2025 | 1.00% (0.01003) | 75.08th | v4 (v2025.03.14) |
| Nov 4, 2025 | 4.59% (0.04586) | 88.72th | v4 (v2025.03.14) |
| Nov 1, 2025 | 2.50% (0.02495) | 84.84th | v4 (v2025.03.14) |
| Oct 28, 2025 | 4.59% (0.04586) | 88.71th | v4 (v2025.03.14) |
| Oct 27, 2025 | 3.04% (0.03038) | 86.17th | v4 (v2025.03.14) |
| Oct 4, 2025 | 4.59% (0.04586) | 88.76th | v4 (v2025.03.14) |
| Sep 4, 2025 | 3.12% (0.03120) | 86.34th | v4 (v2025.03.14) |
| Sep 1, 2025 | 1.64% (0.01636) | 81.27th | v4 (v2025.03.14) |
| Aug 4, 2025 | 3.04% (0.03038) | 86.15th | v4 (v2025.03.14) |
| Aug 1, 2025 | 1.64% (0.01636) | 81.25th | v4 (v2025.03.14) |
| Jul 30, 2025 | 3.12% (0.03120) | 86.33th | v4 (v2025.03.14) |
| Jul 16, 2025 | 5.34% (0.05339) | 89.60th | v4 (v2025.03.14) |
| Jul 11, 2025 | 3.92% (0.03922) | 87.80th | v4 (v2025.03.14) |
| Jul 4, 2025 | 5.27% (0.05271) | 89.54th | v4 (v2025.03.14) |
| Jul 1, 2025 | 2.71% (0.02707) | 85.32th | v4 (v2025.03.14) |
| Jun 4, 2025 | 5.27% (0.05271) | 89.49th | v4 (v2025.03.14) |
| Jun 1, 2025 | 2.71% (0.02707) | 85.23th | v4 (v2025.03.14) |
| May 4, 2025 | 5.27% (0.05271) | 89.44th | v4 (v2025.03.14) |
| May 1, 2025 | 2.71% (0.02707) | 85.13th | v4 (v2025.03.14) |
| Mar 30, 2025 | 5.27% (0.05271) | 89.03th | v4 (v2025.03.14) |
| Mar 29, 2025 | 8.01% (0.08013) | 86.57th | v4 (v2025.03.14) |
| Mar 17, 2025 | 5.27% (0.05271) | 89.29th | v4 (v2025.03.14) |
| Jul 20, 2024 | 0.54% (0.00541) | 77.54th | v3 (v2023.03.01) |
| Feb 8, 2024 | 0.54% (0.00541) | 76.62th | v3 (v2023.03.01) |
| May 8, 2023 | 0.54% (0.00541) | 73.90th | v3 (v2023.03.01) |
| Mar 7, 2023 | 0.36% (0.00364) | 67.99th | v3 (v2023.03.01) |
| Mar 6, 2023 | 1.05% (0.01055) | 52.13th | v2 (v2022.01.01) |
| Sep 17, 2022 | 1.05% (0.01055) | 50.47th | v2 (v2022.01.01) |
| Apr 1, 2022 | 1.05% (0.01055) | 48.43th | v2 (v2022.01.01) |
| Feb 4, 2022 | 1.05% (0.01055) | 27.52th | v2 (v2022.01.01) |
| Feb 3, 2022 | 0.98% (0.00976) | 26.54th | v1 |
| Jan 6, 2022 | 0.98% (0.00976) | 25.91th | v1 |
| Sep 1, 2021 | 0.98% (0.00976) | 61.78th | v1 |
| Apr 14, 2021 | 0.98% (0.00976) | 0.00th | v1 |
References (7)
- http://www.securityfocus.com/bid/98518 vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry
- https://access.redhat.com/security/cve/CVE-2017-8923 Vendor Advisory
- https://bugs.php.net/bug.php?id=74577 x_refsource_MISCExploitIssue TrackingVendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1451700 Issue Tracking
- https://nvd.nist.gov/vuln/detail/CVE-2017-8923
- https://security.netapp.com/advisory/ntap-20241227-0007/
- https://www.cve.org/CVERecord?id=CVE-2017-8923
| Link | Providers | Tags |
|---|---|---|
| http://www.securityfocus.com/bid/98518 | vdb-entryx_refsource_BIDThird Party AdvisoryVDB Entry | |
| https://access.redhat.com/security/cve/CVE-2017-8923 | Vendor Advisory | |
| https://bugs.php.net/bug.php?id=74577 | x_refsource_MISCExploitIssue TrackingVendor Advisory | |
| https://bugzilla.redhat.com/show_bug.cgi?id=1451700 | Issue Tracking | |
| https://nvd.nist.gov/vuln/detail/CVE-2017-8923 | ||
| https://security.netapp.com/advisory/ntap-20241227-0007/ | ||
| https://www.cve.org/CVERecord?id=CVE-2017-8923 |
Change history (0)
No recorded changes yet.