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Two critical PHP remote code execution vulnerabilities will be patched in an emergency release on October 21. Fixes are only expected for supported PHP 8.x branches. Key takeaways CVE-2026-109618 and CVE-2026-109619 are critical vulnerabilities in PHP, both rated CVSSv4.0 9.2 by the PHP security team. Public reporting describes both as remote code execution vulnerabilities. watchTowr says it believes it has reproduced CVE-2026-109618, and Cloudflare CTO Dane Knecht says the company is seeing early attacks emerging. The patch release is scheduled for October 21, 2026 at 14:00 UTC. Version numbers reported before the release point to PHP 8.5.12, 8.4.27, 8.3.36 and 8.2.35. End-of-life branches are not expected to receive fixes. Background Tenable's Research Special Operations (RSO) team has compiled this blog to answer Frequently Asked Questions (FAQ) regarding two critical vulnerabilities in PHP that were announced on October 20, 2026. FAQ When were these PHP vulnerabilities first disclosed? On October 20, 2026, the CVE identifiers circulated on Hacker News and social media. Later that day, the PHP security team published an advance notice of a security release scheduled for October 21 at 14:00 UTC (10:00 AM ET) to address two critical vulnerabilities. The notice said the team could release earlier if details became public or if exploitation appeared in the wild. CERT-EU also published an advisory (2026-018) naming both CVEs. According to watchTowr , the vulnerabilities were originally set to be disclosed on Thursday, October 22, under embargo. A video shared by researcher Kirill Firsov demonstrates the exploit chain, dubbed php2shell. Firsov credited the video and exploit to researcher LCFR and Calif.io. The PHP security team is giving advance notice: Upcoming security release Wed, Oct 21st 2026, 14:00UTC, two critical vulnerabilities, both rated CVSSv4 9.2. PHP users are encouraged to prepare to update. Earlier release if details become public or active exploit evidence. — The PHP Foundation (@ThePHPF) October 20, 2026 What are CVE-2026-109618 and CVE-2026-109619? CVE Description CVSSv4.0 CVE-2026-109618 Unspecified PHP Vulnerability 9.2 CVE-2026-109619 Unspecified PHP Vulnerability 9.2 CVE-2026-109618 and CVE-2026-109619 are critical vulnerabilities in PHP. Public reporting describes both as remote code execution vulnerabilities. The PHP security team has not published technical details before the patch release. CVSS scores differ across sources. The PHP security team rates both vulnerabilities as CVSSv4.0 9.2. Some early reports, including watchTowr and a Hacker News post, describe them as CVSS 10.0. We will update this blog once PHP publishes its advisory. Which PHP versions are affected? CERT-EU says these vulnerabilities could affect all PHP versions from PHP 5 onwards, and the demonstration video references PHP 5.4.0 and later. PHP will publish the official list of affected and fixed versions with the release. Before the release, security researcher Kevin Beaumont reported the following fixed versions: Affected Versions Fixed Version (expected) PHP 8.5.x 8.5.12 PHP 8.4.x 8.4.27 PHP 8.3.x 8.3.36 PHP 8.2.x 8.2.35 PHP 5.x through 8.1.x End-of-life, no fix expected Linux distributions that ship older PHP packages may backport fixes, so organizations using distribution packages should check their vendor's advisories. How widespread is PHP, and how many hosts are potentially affected? According to W3Techs , PHP is used by 69.3% of websites whose server-side language is known. Platforms such as WordPress, Drupal, Joomla, Laravel and Magento all run on PHP. Security researcher Silas Cutler's rough estimate is that over 1.3 million internet-exposed hosts are potentially vulnerable. A Shodan search by Henk Poley counts over 1.9 million internet-exposed hosts running PHP. Has exploitation been observed in the wild? On October 21, Cloudflare CTO Dane Knecht said the company is "seeing early attacks emerging" and is updating its miti…

Algorithm::UrataniTakeda versions from 0.1.5 before 0.1.7 for Perl allow memory exhaustion via a never-cleared failure shift cache in search. The failure shift is cached for each pair of trie state and text character in a field of the matcher object, and nothing clears it. A character not seen before at a given state adds an entry that lasts for the life of the matcher. An attacker who can submit text with many distinct characters to a long-lived matcher can grow its memory with each search.

Pillow is a Python imaging library. From 9.4.0 until 13.0.0, ImagingJpegEncode() in src/libImaging/JpegEncode.c can call jpeg_write_marker() for a JPEG COM comment when an ICC profile has exactly filled the 65536-byte encoder buffer. libjpeg writes one byte before checking the exhausted free_in_buffer counter, which then wraps and permits the attacker-controlled comment and subsequent compressed image data to overwrite adjacent heap memory. Re-saving an untrusted image as JPEG while preserving its ICC profile and forwarded comment can crash the process and may enable code execution in suitable runtime and heap layouts. This issue is fixed in version 13.0.0.

The system certificate authority (CA) store in Red Hat products, distributed via ca-certificates RPM packages, included multiple root CA certificates of authorities, which signed intermediate CA certificates with weak private keys issued by the eMudhra certificate authority. A man-in-the-middle attacker could use this flaw to issue certificates for arbitrary host names signed by the weak intermediate CA certificates, which would be considered trusted by a TLS/SSL client using system CA store and cause such clients to connect to malicious sites. Due to inability to only distrust specific intermediate certificates in all clients using the system CA store, root CA certificates of authorities that signed weak intermediate CA certificates are being removed.

Pillow is a Python imaging library. From 11.0.0 until 13.0.0, Exif.load() in src/PIL/Image.py repeatedly slices the remaining EXIF data while it begins with the six-byte Exif header. src/PIL/PngImagePlugin.py accepts an uncapped PNG eXIf chunk, so a file filled with repeated headers causes a new shrinking copy on every iteration and quadratic CPU work. The condition is reachable through Image.getexif(), Image._getexif(), and ImageOps.exif_transpose(), including common photo-upload rotation workflows. This issue is fixed in version 13.0.0.

Pillow is a Python imaging library. Prior to 13.0.0 on Windows, src/PIL/WmfImagePlugin.py passes unchecked 32-bit WMF or EMF dimensions to the native drawwmf handler in src/display.c. The handler sizes a DIB allocation from 16-bit-truncated bcWidth and bcHeight fields but copies pixel data using the original full dimensions. A crafted wide, short metafile can pass the pixel-count decompression-bomb check and make the Windows-only renderer read beyond the heap buffer, potentially disclosing memory or crashing the process. This issue is fixed in version 13.0.0.

CVE-2026-96641 is an integer overflow vulnerability in the python-pillow Pillow library prior to version 13.0.0. The flaw occurs in the PILfont text-width accumulation code where negative glyph advances are not properly checked against the minimum integer limit, allowing a signed 16-bit advance of -32768 to cause an integer overflow. This can lead to logic errors or excessive resource consumption in applications using text layout or size calculations. The issue is fixed in Pillow version 13.0.0.

CVE-2026-96642 is a high-severity vulnerability in the python-pillow Pillow library prior to version 13.0.0. It involves an infinite loop in the TarIO initializer when processing a negative octal member size, causing the parser to repeatedly read the same header and consume a full CPU core without returning. This issue occurs only when applications directly use PIL.TarIO.TarIO, not the default Image.open() path. The vulnerability is fixed in Pillow version 13.0.0.

CVE-2026-82987 is a vulnerability in the ViewSonic vCast media streaming service used in ViewSonic ViewBoard devices. It involves missing authentication on critical screen capture endpoints (/snapshot or /screen), allowing remote unauthenticated attackers to capture and exfiltrate the current screen content as JPEG images. This affects versions from 0.0.0 up to and including 3.2.715. No CVSS score is provided, and no known exploits are reported in the wild. No patch or official remediation details are currently available from the vendor advisory.

A vulnerability in the Pillow Python imaging library versions 9.1.0 through 12.x allows crafted RLE BMP images to cause uncontrolled resource consumption. Specifically, the BmpRleDecoder.decode() function can append data beyond expected limits, leading to excessive memory allocation and potential denial of service. This issue is resolved in version 13.0.0.